In the transfer of large quantities of particulate solids, such as grain and the like, such as the transfer from one storage location to a transporting vehicle or vessel, a flow of grain is normally controlled through enclosed columns or conduits, with the conduits having a discharge chute or opening at the lower end thereof. The movement or flow of the grain is analogous to fluid flow, and entrained air frequently causes a cloud of dust to be generated at the discharge end of the column or conduit.
Two basic techniques may be utilized to reduce the quantity of air-borne dust emitted during the discharge delivery, one being to reduce or prevent the generation, the second being to collect, capture, or otherwise control the environment in which the dust generation occurs. The present system utilizes a combination of these two basic techniques, including the utilization of a shroud means for collection of dust, along with the generation of a flow pattern which reduces the severity of interaction of the grain kernels outside of the controlled or confined shroud area. When the dust is collected, separation of the solid particles from the supporting air is conducted in a solid-air separator or the like such as a filter chamber or the like.
In the handling of grain, a typical operation includes the transfer of the grain from an elevator structure to the hold of a transporting vehicle, such as for example, a ship, barge, or the like.
The structural features of the various vessels into which grain is loaded and transported vary considerably. For example, in the typical grain transporting barges, three basic and different designs are utilized, including, for example, the typical open-top barge, a hatched barge having oval-shaped openings for access to the hold, and a barge having a hatch with rectangular metal openings formed in the hatch. In open-top barges, the cargo is shielded or protected with sliding panels, and these structures constitute approximately 50% of the grain transport barges in use at this time. This design provides the greatest degree of flexibility in loading, inasmuch as the cargo area is easily reached with a typical discharge spout, and the grain may be loaded into the barge relatively easily.
In handling of grain, flow characteristics and patterns must be considered in order to reduce the risk of damage to the product. In particular, the fracturing of individual grain kernels must be held to a minimum.
It will be appreciated that the location of the grain supply is fixed, and the location of the receiving vessel is variable. Therefore, the angle at which the discharge chute is maintained during loading may vary from about 45.degree. to about 70.degree. from the horizontal, thereby providing a significant variation in discharge velocity of the grain being moved through the discharge chute.
The generation of dust in a grain loading operation is substantial. Dust is raised or otherwise emitted whenever the velocity of the ambient air is sufficient to support the particulate matter. This air velocity is a function of a number of variables including, for example, wind, secondary air currents caused by momentum transfer from the grain, or mechanically produced air flow. The first two variables contribute to the generation and emission of dust during a grain operation, while the third is usually associated with the collection of dust. The present arrangement provides a structural arrangement including a shroud which controls the flow of the secondary air currents generated by momentum transfer, and utilizes these secondary air currents for a useful purpose and function in the removal of air-borne dust.
In the past, attempts have been made to control dust emission by utilizing a reverse air flow through a portion of the delivery conduit or column, or by immersing or otherwise burying the delivery spout into the grain accumulated at the end of the chute. Still another technique involves controlling dust by covering the open area of the receiving vessel with a tarpaulin or the like, and controllably exhausting the air outwardly through a remote collection system. Still another technique involved the placing of a hood or the like over the discharge end of the chute and exhausting air through this hood. Each of these techniques involved difficulties, such as causing a clogging of the spout or conduit, a failure to significantly reduce the emission of dust, or imposes limitations on the type of vessels or receivers used.
In accordance with the present invention, a system is provided for controlling the emission of air-borne dust, with the system being adapted for use in any of the conventional transporting vessels. Briefly, the discharge end of the conduit or column is provided with an enclosing shroud with an open bottom wall which defines the ultimate discharge opening. An angularly disposed lead-in flow diverter plate is provided so as to at least partially change the direction of flow of the grain to a more horizontally disposed path with a consequent virtual momentary elimination of any vertical downward velocity component. The edge of the lead-in flow diverter plate forms one edge surface of the discharge opening. At the opposed edge surface of the discharge opening, an abutment plate is interposed so as to intersect the normal flow path of the grain as it passes from the edge surface of the flow diverter plate. The grain, when passing across the span between the edge of the flow diverter plate and the abutment plate forms a "dynamic seal" between the ambient and the upper enclosed volume of the spout enclosing shroud, thus confining a substantial portion of the dust generated within the enclosed shroud. A duct is coupled to the upper portion of the spout enclosing shroud, with this duct, being in turn coupled at its other end to a solid-air separator means. Air flow between the enclosed shroud and the solid-air separator means is achieved to a substantial extent by virtue of the mechanically produced air flow resulting from the grain passing through the enclosed column.
In addition to its effective dust control, this system is versatile in that it finds utility in connection with the barge top variations in present use, and also causes little, if any, damage to the grain passing through. The system is energy efficient in that it utilizes the energy developed from the descending grain for achieving a flow of air useful in carrying the collected or captured dust to a solid-air separator.